Drive Shift Design Claims to Have Perfected the 3-Speed Electric Vehicle Transmission

4 years ago by Eric Loveday 12

DSD 3-Speed/ Complete EV Powertrain Mock Up

DSD 3-Speed/ Complete EV Powertrain Mock Up

The multi-speed transmission has not quite lived up to the hype when dropped into an electric vehicle.

Different Angle of Mockup

Different Angle of Mockup

Sure, there are limited pure electric applications out there that have made successful use of a multi-speed setup.  But, by and large, the single-speed remains the go-to choice for BEVs.

Will that change soon?

Specialist engineering consultancy, Drive System Design (DSD), seems to think so.

DSD is currently developing a three-speed transmission for next-generation hybrid and electric vehicles. Called MSYS, the system uses the “powershift principle to overcome torque interruption during shifts, providing ultra smooth shifting.”

DSD says a multi-speed transmission enables an electric vehicle to either achieve higher performance or increased range.  This is made possible by more efficient motor use, as compared to a conventional single-speed trans setup.

DSD promises smooth shifts, too:

“Most transmissions have a step between ratios of 2.0:1 or more.  We identified that there is a threshold value of around 1.5:1, below which the shift event can be made to feel imperceptible to the driver and occupants through accurate control of the powershift actuators.”

There are other benefits to the MSYS, too.  DSD claims “MSYS provides a 40 percent weight saving and 10-15 percent lower vehicle energy consumption, because it permits downsizing of the motor and, by being in the optimum gear ratio more often, extends the time the motor spends operating at high efficiency.”

There are 2 ways in which in 10-15 percent reduction in energy consumption can be applied:

“The reduced vehicle energy consumption can be taken as a 10-15 percent increase in range, or a saving of 10-15 percent in battery size.”

DSD says that the MSYS transmission will be put into a demonstration vehicle in Q4 of 2013.

See below for full specs on the proposed MSYS trans/motor setup.

DSD Full Spec Sheet

DSD Full Spec Sheet

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12 responses to "Drive Shift Design Claims to Have Perfected the 3-Speed Electric Vehicle Transmission"

  1. alohart says:

    Adding a transmission to an EV would increase its complexity, maintenance requirements, potential repair costs, and initial cost while decreasing its reliability. I’m not sure whether the 10-15% greater efficiency would offset those disadvantages.

  2. Spec says:

    Transmissions can definitely add some performance . . . but I just don’t think it is worth it. Adding a transmission adds cost and complexity to an already expensive EV with little received in return. So I don’t see the point unless you are trying to build a very expensive high-performance EV.

  3. kdawg says:

    At the end of the day, does in increase or decrease the cost of the EV?

  4. Aaron says:

    Tesla’s Roadster had a two-speed transmission when it first came out. Due to transmission failures, they took the transmission out, opting for a single-speed reduction gear. I have to agree with the above posters and say that the 10-15% increase ain’t worth it. Not to mention, how much of that is lost in the transmission’s 9% loss right off the top?

    1. Bill Howland says:

      They weren’t super clear about this but I’m assuming when they say “overall 91% efficiency”, they are including the motor inefficiency, therefore 91% ain’t that bad.

      I’m satisfied with the Synergy Drive in my 2011 Volt. Very very smooth. And helical gearing keeps it quiet and efficient. I suspect its a bit pricey though… 2 motors, 3 clutiches, and hydraulic servos, and at least one oil pump.

      1. Foo says:

        Yeah, but the Volt needs a transmission of some kind because it has a complex system for connecting the gas engine to the drive train (for freeway speeds) as well as to the generator.

        I agree with the other posters… for a pure EV, the use of any kind of transmission (for varying speeds) seems dubious. Just having a transmission in the system alone adds friction, not to mention weight.

        I think research funds/time would be better spent developing advanced electric motors that are more efficient/powerful over a wider range of speeds. Motors that simply connect directly to the wheels. This will result in the lightest, simplest, and most reliable vehicles.

  5. Fluke says:

    Hopefully they would be able to scale this up to handle more horsepower and torque. The indicated specs (80Hp continuous, 114 Hp intermittent, 148 lb-ft) would probably not handle any of the current highway capable EV’s except maybe the Mitsubishi i.

  6. Roy_H says:

    There is a far more elegant way to incorporate a “transmission” with an electric motor. Design the motor with multiple windings that can be powered in series/parallel or one only. This is not a new idea, and has been considered by most auto manufacturers. Their evaluation is that it is not worth it. The Volt is sort of like this with its two electric motors.

    What DSD is claiming is that a smaller motor can provide the same performance as a bigger one if they use their transmission. First a smaller motor will not deliver the ultimate power required for highway passing no matter how magical the transmission is. Second it is really cheap to scale up an electric motor, so cost savings suggested are just not there.

    Their only possible market is for auto companies that buy off the shelf electric motors and cannot get the size/features they really want.

  7. What does it say about the design that the motor is about half the size of the transmission? The motor is about the same size as the differential.

    Ironically, the YASA motor is designed to be direct drive. With two YASA motors back to back, each driving a wheel directly through a drive shaft – what would the efficiency and the torque then?

    Neil

  8. Brian says:

    This seems to me like a company hinged on older technology trying to force what they know into what they think is the future, not trying to solve any actual problem. I suspect we will see more of this as EVs become more prominent, and the threat to ICEV dominance because more tangible.

  9. Adding gears may lower manufacturing costs, but what about performance and reliability?

    More gears in a transmission allows a larger, lower power rated, and easier to manufacture electric motor to be used. Why not put money into improving the electrical motor vs. tacking on a bunch of extra moving parts prone to failure? The traditional engineering application for transmission is to stretch the power curve, but power curve of electric motor is already a constant 90+%

    Compare size and reliability of Tesla Motors 400+ HP electric motor to the more common 100 HP motors. How does Tesla put the power of a V8 ICE engine into size of a cubic foot? Note: gears between Tesla Motor are about 3x wider than traditional gears to handle the 100% electric motor toque. Most normal (smaller ICE) gears will suffer under low RPM, high torque.

    Engineering simpler solutions takes more upfront time and money, but saves cost and pain in long run.

  10. Martin T says:

    Wrong approach.
    Ultimate will be: light weight “in wheel” motors – that’s the future.
    Gearboxes with their inherent losses a big no no.

    I believe motor technology – especially motor control will WIN the day
    In the end making gearboxes and drive shafts obsolete except for construction machinery and even then …